Individuals between two weeks to twenty years of age who have an HIV and cytomegalovirus are enrolled in this study to evaluate the safety and side effects of a new oral medication, ganciclovir. The purpose of this study is to determine if an oral form of ganciclovir can be tolerated when given for 24 weeks to HIV infected infants and children with CMV infection and to determine the maximum tolerable dose and side effects of oral ganciclovir.